Browsing by Author "Li, Xiang"

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    Critical Thinking in International Contexts: Poly-Ethnographic Accounts of Multicultural Research Collaboration
    (University of Calgary, 2016-05) Woodend, Jon; Fedoruk, Lisa; Beek, Avis; Wu, Xueqin; Roy, Sylvie; Groen, Janet; Li, Xiang; Werklund School of Education
    In December 2015, selected doctoral students and faculty from Queensland University of Technology (QUT) and the University of Calgary (U of C) participated in a seminar hosted by Beijing Normal University (BNU) for interdisciplinary/international collaboration. In this paper the U of C participants outlined their reflections of this experience through a poly-ethnographic approach, with consideration for the Twelfth Dimension Framework for School Systems Success. The main themes that emerged included the role of culture and the impact of power dynamics when working academically on an international level.
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    Design of Multi-band/Wide-band High Efficiency Power Amplifiers
    (2018-04-18) Li, Xiang; Helaoui, Mohamed; Belostotski, Leonid; Kim, Bumman; Ghannouchi, F. M.; Fear, Elise C.; Alhajj, Reda S.
    As an important component of the RF front-end in the transmitter, the power amplifier (PA) is used to convert the DC supply power into RF power. As the PA consumes most of the power in the transmitter, minimizing power dissipation of the PA would have a significant effect on the efficiency of the whole system. During recent decades, several works have been done to enhance the PA efficiency. However, there must be a trade-off between efficiency, linearity, gain, output power and bandwidth, which are five crucial attributes of the PA. With the development of the wireless communication system, multiple standards at different frequency bands are highly demanded to be integrated into one system while the increasing data rate requires a wide frequency spectrum and therefore broadband components. The multi-band/wide-band signals also lead to high peak-to-average power ratio. Thus, PAs are required to operate at multi-band/wide-band with high efficiency within a wide output power back-off (OPBO) range. For this reason, this thesis focuses on the PA theory and design method for multi-band, wide-band and wide-OPBO purpose. For the first time, a quad-band impedance inverter with arbitrary frequency ratio is proposed. Based on this impedance inverter, a concurrent quad-band Doherty has been designed at 0.75GHz, 1.75GHz, 2.65GHz and 3.55GHz with efficiency up to 50% at 6dB OPBO. For the first time, this thesis present a new theory for harmonically tuned PAs with maximally flat waveform, named class X PAs. The theory was developed for arbitrary harmonic tuning with arbitrary number of harmonics. The analytic close-form formulas for the voltage and current waveforms are provided. Design space for the Class-X PA with only first three harmonics is derived. To validate the theory, a wide-band PA has been designed with output power above 38dBm, efficiency higher than 70% over an octave bandwidth. The harmonic tuning method is also applied to the outphasing system in order to improve the efficiency. A harmonically tuned class-F outphasing system at 27.1MHz is designed with three third harmonic tuning cases to validate the theory. A harmonically tuned class-F-1 outphasing system at 2.14GHz is designed with efficiency of 68% at 6dB OPBO
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    Embeddedness through Utilitarianism: An Example of Cultural Identification of Post-85s in Alberta
    (2016-01-29) Li, Xiang; Steinberg, Shirley; Donlevy, Kent; Lenters, Kimberly
    This research study utilizes the theoretical perspective of critical inquiry, and employs multi-disciplinary methodologies within a critical bricolage, to contextualize Christotainment in Alberta, Canada, analyze its nature, and the reasons for its acceptance by Chinese Post-85s (people who were born between 1985 and 1990 in China), and examine its effects. The compound word of Christotainment refers to the merging of “Christ” and “entertainment”, indicating the socio-political and socio-cultural marketing of Christian fundamentalism. The findings are as follows: a) Christotainment to Chinese Post-85s in Alberta represents a power of cultural embeddedness; b) The motivations for the involvement of Chinese Post-85s in Alberta in Christotainment are both external and internal due to the utilitarian characteristics of their cultural identification; c) The embedding effect of Christotainment on Chinese Post-85s in Alberta imposes upon the Chinese a Western cultural hegemony characterized by its ostensibly profiteering purpose. At the same time, bricolage as methodology opened possibilities for alternative understanding as the study unfolded and the author wrote about struggles, confusion, emotions, and her personal achievement, as well as that of the interviewees during the four-and-a-half-years of exploration. The study is constantly in progress with the pace of the constantly shifting values and cultural identity of the special group of Chinese Post-85s in Alberta.
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    Embeddedness through Utilitarianism: An Example of Cultural Identification of Post-85s in Alberta
    (2016-01-29) Li, Xiang; Steinberg, Shirley; Donlevy, Kent; Lenters, Kimberly
    This research study utilizes the theoretical perspective of critical inquiry, and employs multi-disciplinary methodologies within a critical bricolage, to contextualize Christotainment in Alberta, Canada, analyze its nature, and the reasons for its acceptance by Chinese Post-85s (people who were born between 1985 and 1990 in China), and examine its effects. The compound word of Christotainment refers to the merging of “Christ” and “entertainment”, indicating the socio-political and socio-cultural marketing of Christian fundamentalism. The findings are as follows: a) Christotainment to Chinese Post-85s in Alberta represents a power of cultural embeddedness; b) The motivations for the involvement of Chinese Post-85s in Alberta in Christotainment are both external and internal due to the utilitarian characteristics of their cultural identification; c) The embedding effect of Christotainment on Chinese Post-85s in Alberta imposes upon the Chinese a Western cultural hegemony characterized by its ostensibly profiteering purpose. At the same time, bricolage as methodology opened possibilities for alternative understanding as the study unfolded and the author wrote about struggles, confusion, emotions, and her personal achievement, as well as that of the interviewees during the four-and-a-half-years of exploration. The study is constantly in progress with the pace of the constantly shifting values and cultural identity of the special group of Chinese Post-85s in Alberta.
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    Optimal Portfolios of Natural Gas Futures
    (2021-01-28) Li, Xiang; Ware, Antony Frank; Swishchuk, Anatoliy V.; Qiu, Jinniao
    In this thesis we investigate portfolios consisting of a collection of positions in natural gas futures. The logarithms of the futures prices follow correlated Ornstein-Uhlenbeck processes which are mean-reverting. Under the assumption that the portfolios are constant and short-selling is allowed, formulae for the portfolio that is optimal in terms of minimizing Capital at Risk (CaR) in a continuous-time context are obtained following an adapted version of the theory in [14]. We show that the results in this paper hold with small modifications in our situation and we apply them to portfolios of positions in AB NIT natural gas futures contracts. Furthermore, we allow the portfolio to be reoptimized periodically, showing dramatically better performance of portfolio with regard to the final wealth. And finally we consider the contract size limitation so that the portfolio is tradeable, and demonstrate the unsurprising underperformance of the portfolio that results.